Gemcitabine and Carboplatin With or Without AZD2171 as First-Line Therapy in Treating Patients With Stage IIIB or Stage IV Non-Small Cell Lung Cancer

RATIONALE: Drugs used in chemotherapy, such as gemcitabine and carboplatin, work in different ways to stop the growth of tumor cells, either by killing the cells or by stopping them from dividing. AZD2171 may stop the growth of tumor cells by blocking some of the enzymes needed for cell growth and by blocking blood flow to the tumor. Giving gemcitabine and carboplatin together with AZD2171 may kill more tumor cells. PURPOSE: This randomized phase II trial is studying how well giving gemcitabine and carboplatin together with AZD2171 works compared to giving gemcitabine and carboplatin without AZD2171 as first-line therapy in treating patients with stage IIIB or stage IV non-small cell lung cancer.